@Skud if you google 'contribute to rails docs' you get this page, which has a link to docs:

Ruby on Rails is not “someone else’s framework.” Over the years, hundreds of people have contributed to Ruby on Rails ranging from a single character to massive architectural changes or significant documentation. All with the goal of making Ruby on Rails better for everyone. Even if you don’t feel up to writing code or documentation yet, there are a variety of other ways that you can contribute, from reporting issues to testing patches.